TLR7 REGULATES SELECTION OF GERMINAL CENTER B CELLS AND AUGMENTS THE GENERATION OF MUTATED B MEMORY DURING THE PRIMARY RESPONSE

TLR7;Germinal Centers;B cell Memory Germinal Center B cells;B cell Selection;Immunology

Castiblanco, Diana P.Siliciano, Robert F. ;

Johns Hopkins University

关键词: TLR7;    Germinal Centers;    B cell Memory Germinal Center B cells;    B cell Selection;    Immunology;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/39726/CASTIBLANCO-DISSERTATION-2016.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

Recent work has demonstrated the importance of Toll-Like Receptor 7 (TLR7) in generating protective antibodies against viral infections. However, how TLR7 stimulation modulates mechanisms like somatic hypermutation and selection of B cells- so crucial for the generation of high affinity antibodies and memory- still need to be studied. Here, we demonstrate a role for TLR7 in the regulation of germinal center B cell selection and memory generation. We used a reductionist system to determine the effect of one TLR ligand on the germinal center reaction by immunizing mice intraperitoneal with nitrophenyl-chicken gamma globulin (NP-CGG) in the presence or absence of R837, a TLR7 agonist.To test the effect on somatic hypermutation, germinal center B cells were isolated, cDNA encoding NP-specific IgH variable genes was sequenced, and activation-induced deaminase (AID) mRNA was measured. While AID expression was the same in both sets of mice, the mutation frequency and proportion of high affinity clones was significantly higher in mice that received TLR7 agonist. This observed phenomenon suggested that TLR7 played a role in selection of antigen-specific germinal center B cells. To further examine selection, the apoptotic profile and distribution of B cells in the light zone of the germinal center was examined.The total number of apoptotic B cells in the light zone was four fold lower in mice who received TLR7 agonist.However, the distribution of B cells in the light zone remained the same in both sets of mice, indicating that selection into the memory compartment had taken place.Mice that received TLR7 agonist had an enhanced ability to generate IgM B cell memory. When total naïve wild type or TLR7 knockout B cells were transferred into µMT mice- lacking mature B cells- an enhanced ability to generate NP-specific mutated memory was observed in mice receiving TLR7 agonist. However, when TLR7 knockout B cells were transferred, this enhanced ability was ablated indicating that B cell intrinsic signaling of TLR7 was required for augmented memory generation. Together this data demonstrates that TLR7 intrinsically regulates germinal center B cell selection and memory generation during the primary response.